The present invention relates to a Voice over DSL (VoDSL) architecture for supporting a xe2x80x9clifelinexe2x80x9d service. More particularly, the present invention is directed to a system and method for providing a telephone service to a VoDSL customer despite an electrical power outage or integrated access device failure at the customer premise.
Due to recent changes in the telecommunications industry (i.e., deregulation of local markets) and recent advancements in technologies that better utilize the existing copper loop infrastructure, digital subscriber line (DSL) is one of the most promising technologies for delivering viable low-cost, high-speed data to many business and residential customers. As is well known, DSL uses the existing copper loop that is traditionally used for conventional telephony to deliver voice and data at high bandwidth. DSL carries both voice and data signals simultaneously, in both directions, allowing a customer to log onto the Internet and make a telephone call at the same time. In other words, since DSL uses packet switching technology that operates independently of the voice telephone system, this allows telephone companies to provide Internet service and not lock up circuits for telephone calls. Thus, it is easy to understand why DSL technology is becoming the preferred method for sending/receiving both voice and digital data/signals in the telecommunications industry.
As is well known, there are different competing forms of digital subscriber line technologies collectively designated as xDSL technologies with the xe2x80x9cxxe2x80x9d representing various one or more letter combinations, which are used in front of the xe2x80x9cDSLxe2x80x9d acronym to designate the type of technology being used. Some of the more prevalent xDSL technologies include HDSL, ADSL, SDSL, RADSL, VADSL, and VDSL.
One particular technology known as Voice over DSL (VoDSL) provides multiple phone channels to be delivered over a DSL line, which itself is delivered over a single copper pair. Using VoDSL, multiple servicesxe2x80x94voice, data, fax, video conferencing, etc.xe2x80x94can be delivered over the single copper pair. In other words, by enabling up to, for example, 24 telephone channels (can be more or less than 24) and high-speed Internet access (typically at speeds up to 1.5 megabits per second) to be delivered over a single DSL connection, VoDSL systems allow service providers to apply DSL broadband access networks to small to mid-size business markets and residential homes. VoDSL essentially turns one copper pair into multiple telephone channels and one high-speed data channel. This substantially lowers the infrastructure cost for delivering such services when compared to T1 lines or multiple copper pairs.
FIG. 1 illustrates a simplified diagram of a conventional VoDSL architecture. In the conventional architecture, a regional switching center is connected to a customer premise (residential, business, small office/home officexe2x80x94SOHO, etc.) via a central office (CO) and a copper loop 10 (pair of copper wires). In the customer premise, an integrated access device (IAD) 12 (perhaps in a wiring closet) is connected to a data terminal such as the PC and multiple voice terminals such as telephones PH-1, . . . , PH-m, where m is some arbitrary number of channels/telephones. As known, the IAD 12 delivers both voice and data services to the customer and is described in greater detailer later herein.
The IAD 12 is connected to a DSL access multiplexer (DSLAM) 8 at the CO via the copper loop 10. As known, the DSLAM 8 generally receives incoming DSL signals and aggregates the traffic onto high-speed uplink trunks such as DS3 or SONET optical link.
In the regional switching center, an ATM (asynchronous transfer mode) switch 6 is connected to the DSLAM 8 via the high speed trunk such as DS3 or SONET optical link. ATM is a high-speed networking standard used in WANs and often used to route DSL traffic to the Internet backbone. One ATM switch 6 can be connected to many DSLAMs (hundreds, thousands) 8, which in turn, can support many IADs 12. The ATM switch 6 is further connected to a data network (e.g., Internet) and a public switched telephone network (PSTN) via a voice gateway 4 and a Class 5 voice switch (C5) 2.
The C5 switch 2, gateway 4, ATM switch 6, and DSLAM 8 are well known in the industry and thus will not be discussed in great detail. Communication interface between the gateway 4 and the C5 switch 2 is through an interface standard such as TR-303 or TR-008. The TR-303 and TR-008are standard interfaces developed for the North America PSTN for inter-working of voice switches and digital loop carrier (DLC) systems.
The C5 switch 2, gateway 4, ATM switch 6, DSLAM 8, and IAD 12 are conventionally known as network elements in the reference model for the conventional architecture. The IAD 12 is not an independent network element per se, but rather a subtending subsystem to the gateway 4. Thus, the gateway 4 and the subtending IAD 12 form an independent network element. Each gateway 4 and C5 switch 2 can support multiple IADs 12, depending on their capacities.
Associated with each network element is a software program generically known as an element management system (EMS), which manages the operation of each network element. The operation, administration, and maintenance (OAM) functions of the VoDSL network is performed by an operation support system (OSS) which supports the C5 switch 2, and works in conjunction with the EMSs for managing the gateway 4 and DSLAM 8. The OSS controls and coordinates all the network elements.
During operation, the IAD 12 receives, digitizes, packetizes, compresses the voice and data signals and formats them for transmission from the customer. The IAD 12 then sends the voice and data signals out in separate virtual circuits, with the voice circuit getting priority. Virtual circuits are connected to the DSLAM 8, which combines virtual circuits from multiple customers and/or IADs 12 and send them to the ATM switch 6 in the regional switching center. The ATM switch 6 then sends the data signals to the data network such as the Internet and the voice signals to the voice gateway 4. The gateway 4 decompresses and depacketizes the signals and sends them to the C5 switch 2, which signals are then sent to the PSTN.
Conversely, when the signals are sent from the regional switching center to the customer premise, the gateway 4 receives digital voice signals and formats them into packets for transmission to the ATM switch 6. The ATM switch 6 also receives data signals from the data network. These signals are then sent to the IAD 12 through the DSLAM 8 and copper loop 10. The IAD 12 receives the signals and distributes them to the proper terminals.
FIG. 2 illustrates a more detailed diagram of a DSLAM and IAD in the conventional VoDSL architecture of FIG. 1. In greater detail, the DSLAM 8 consists of an ATM interface block (AIB) 20 connected to n-number of ADSL (xDSL) termination unit-CO (ATU-C) 22a, 22i, 22n. Each ATU-C 22a, 22i, 22n is further connected to a loop pair (pair-1, pair-i, pair-n), which terminates at a corresponding IAD-112a, IAD-i 12i, IAD-n 12n. As can be appreciated, there will be n-number of IADs corresponding to n-number of ATU-Cs and loop pairs.
Using IAD-i 12i as an example, it consists of an ADSL (xDSL) termination unit-remote (ATU-R) 30 or similar unit that is further connected to a service interface block (SIB) 32. The SIB 32, which distributes signals to different terminals, is further connected to a data module (DM) 34 for high speed data service to the data terminal (PC) and to m-number of phone modules PM136-1, PMm 36-m, which are connected to multiple telephones PM-1, PM-m, respectively. Currently, m can be any arbitrary number such as 14, 16, 24, so long as the system components can support the m number of telephone lines. Accordingly, the IAD-i 12i typically supports one high-speed data port and m-number of telephone ports.
To fully implement the conventional VoDSL system, power is supplied to the IAD-i 12i using a power supply (PS) 39 (110 Vrms, 60 Hz) from the customer premise because it is not economically feasible to power the IAD-i 12i from a CO battery. In addition, the connecting terminals of the ATU-C 22i and ATU-R 30 to the copper pair are normally capacitively coupled, meaning that there is no DC electrical path. As a result, the PS 39 takes AC power and converts it into DC voltage source to power the electronics within the IAD-i 12i. 
At this point, it is important to point out that the copper pairs connecting the DSLAM 8 to the IADs 12a, 12i, 12n are xe2x80x9cdry.xe2x80x9d In other words, there is no DC current flowing through the copper pairs from the CO to the customer premise in the conventional VoDSL system. Conversely, in a conventional plain old telephone system (POTS), the copper pairs are xe2x80x9cwet,xe2x80x9d which means that there can be DC current flowing through them. Wet cop per pairs are normally connected to the CO battery to provide loop supervision and talk current to the telephone.
There are several major shortcomings and disadvantages associated with the conventional VoDSL architecture. For example, because the IAD is powered from the customer premise, electrical power outage at the customer""s premise results in lost of services, and in particular telephone service to the customer. Further, a failure or defect in particular components of the IAD can also result in lost telephone and data service to the customer. These shortcomings and disadvantages are typically uncommon in the POTS system, since the telephone service is powered by the CO battery rather than power from the customer""s premise.
As a result, power outages and/or IAD failures prevent the customer from using his/her telephone for an unspecified period of time. This can be unacceptable when there is an emergency and 911 service is needed. This lack of a xe2x80x9clifeline supportxe2x80x9d has been viewed by many in the telecommunications industry to be the critical factor inhibiting the widespread deployment of VoDSL technology.
As stated above, the conventional VoDSL architecture is generally workable when there is adequate and stable power at the customer premise, but is found to be inadequate and unworkable when there is a power outage and/or IAD failure/defect at the customer premise. Accordingly, there is a need for a reliable and efficient system and method for providing a lifeline support to a VoDSL customer during a power outage, IAD failure, and the like at the customer premise. The lifeline support is needed to keep a telephone line or xe2x80x9clifelinexe2x80x9d available during emergency or other situations.
In view of the above-described problems of the prior art, it is an object of the present invention to provide a system and method for providing a lifeline support to a VoDSL customer.
It is another object of the present invention to provide a lifeline support to a VoDSL customer using the existing VoDSL architecture.
It is yet another object of the present invention to provide a lifeline support when there is an electrical power outage at the customer""s premise having VoDSL service.
It is a further object of the present invention to provide a lifeline support when there is an integrated access device failure at the customer""s premise having VoDSL service.
It is still a further object of the present invention to provide a system and method for actuating a bypass function in an IAD located at the customer premise.
It is yet another object of the present invention to provide one or more active telephone lines to one or more VoDSL customers when electrical power or IAD failure occurs at the customers"" premises.
These and other objects of the present invention are obtained by providing a bypass function in the IAD located in the customer""s premise. The bypass function is preferably a relay, which can be automatically activated to provide the lifeline support. The relay in the IAD, working in conjunction with systems in the central office and the regional switching center allows the customer to obtain an active telephone line. Electrical power is supplied to the customer""s premise from the central office, thereby allowing the customer to use a telephone line in the traditional manner. The present invention can be implemented for any number of customers and telephone lines.